Under the auspices of NIDA's Behavioral Therapies Development Program, funds are requested to support an efficacy trial evaluating an intervention called "The Teen Marijuana Check-Up" with non-treatment seeking adolescent marijuana users. This proposed research is based on earlier Stage 1a and 1b research completed by the applicants with this intervention. Three hundred adolescents who smoke marijuana (ages 14-19), recruited in four Seattle-area high schools, will be enrolled in the trial. Participants will be recruited either through in-class presentations focusing on marijuana or via referrals from school staff. They will first be assessed regarding use of marijuana, alcohol, and other drugs, as well as pertinent attitudes and goals. Participants will then be randomly assigned to one of three conditions. The experimental intervention is a two-session motivational enhancement treatment. A personalized feedback report, containing information from the participant's assessment as well as normative comparison data, is reviewed, with the Health Educator employing motivational interviewing strategies intended to enhance motivation for reduction or cessation of marijuana use. Specific goals for change and behavior change strategies are discussed with participants who wish support to change their marijuana use. The comparison condition involves two educational sessions focusing on the health and behavioral effects of marijuana. The third condition (delayed treatment control) involves a minimal baseline assessment followed three months later by a reassessment interview. Those assigned to this condition will then be given their choice of either active treatment. Following completion of their two intervention sessions, participants in the two active treatments will be offered an additional four sessions of cognitive-behavioral skills training in which the focus is strategies in quitting marijuana. All participants will be reassessed at 3 and 12 months following their initial assessment interviews.